The actuation lever unit generally comprises one or several levers. Normally, the unit contains at least an internal actuating lever, an external actuating lever and a release lever. In addition, the actuation lever unit also often contains a coupling lever. When the actuation lever unit is acted upon, the locking mechanism can be opened in this way. For this purpose, the release lever typically engages with a pawl of the locking mechanism and lifts it off an associated rotary latch. The rotary latch then opens with the assistance of a spring and releases an engaged locking bolt. As a result, an associated motor vehicle door can be opened.
In case of an accident or in the event of a crash, mentioned above, high acceleration forces generally occur, which can be several times greater than the earth's acceleration. The respective motor vehicle door lock is thus exposed to considerable inertia forces which could cause an unintentional opening of the locking mechanism and thus of the entire associated door lock.
These described scenarios represent considerable hazards for vehicle users. A motor vehicle door opened unintentionally can, for instance, no longer provide any safety devices contained therein, such as a side airbag or side impact protection for the protection of the passengers of the vehicle. For this reason, various measures were already implemented in the past that either block the actuation lever unit or the locking mechanism during occurrence of the described abnormal acceleration forces, e.g. in the event of a crash. In these cases, a so-called inertia lock is used, which is in its rest position under normal operating conditions and is not engaged in the actuation lever unit or the locking mechanism.
A catch lever acting on the actuation lever unit is, for instance, disclosed in DE 197 19 999 A1. The lock or catch lever blocks an opening lever when the described acceleration forces are exerted in case of an accident. For this purpose, the lock or the catch lever and the opening lever are arranged transversely to the swivel direction of the opening lever and are displaceable in relation to each other. In case of a relative displacement caused by increased acceleration forces, the opening lever enters the lock. This aims to prevent unwanted opening in the event of a crash whilst keeping the design simple. A permanent blocking of the opening levers is also generally discussed.
The generic state of the art of DE 19910 513 A1 describes a crash catch on a door lock. This catch contains a pivotable catch lever, which can be pivoted by inertia force around its swivel axis into a blocking position stopping the transmission element.
Also, a counter blocking surface is provided, which is fixed in position.
Not all aspects of the prior art are satisfactory. The systems generally work in that the catch lever blocks the actuation lever unit or locking mechanism only during the occurrence of abnormal acceleration forces, e.g. in the event of a crash. In practical application this can result in incorrect functioning, for instance, in case that the movement of the catch lever is blocked or delayed due to corrosion or ageing, etc. Such functional faults can also not be checked, for instance, as part of maintenance, as the catch lever has to be moved, which is not possible in practical application. The invention aims to remedy this situation.